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  • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
  • C01G53/50—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [MnO2]n-, e.g. Li(NixMn1-x)O2, Li(MyNixMn1-x-y)O2
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  • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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  • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
  • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
  • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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  • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
  • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
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  • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
  • H01M2004/028—Positive electrodes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present application relates to the electrochemical field, and in particular, to a positive electrode material, and a preparation method and uses thereof.
• Lithium-ion batteries have the advantages of a high specific energy, a wide temperature range in which the batteries are applicable, a low self-discharge rate, a long cycle life, good safety performance, and no pollution, and have been used in various fields. Attempts are made gradually all over the world to use a lithium-ion battery as an energy system of automobiles in place of traditional combustion engines.
• lithium iron phosphate (LiFePO 4 ), low-nickel ternary material (LiNi 1/3 Co 1/3 Mn 1/3 O 2 ), and the like that are commonly used at present are unable to fully meet the requirements of a motive power battery on an energy density of a positive electrode material of a lithium-ion battery due to limitations of inherent properties of the material.
• a higher nickel content in a high-nickel ternary positive-electrode material increases the energy density of the batteries. Therefore, the high-nickel ternary positive-electrode material is one of the main research topics of the motive power batteries currently.
• direct side reactions between the positive electrode active material and an electrolytic solution are also escalated drastically, and the cycle performance is deteriorated drastically, thereby becoming one of the bottlenecks of commercial mass production.
• an objective of the present application is to provide a positive electrode material and a lithium-ion battery that adopts the positive electrode material.
• a positive electrode material characterized by a relatively low powder resistivity and a relatively low amount of residual lithium on a surface of the material, the present application reduces a direct current impedance, suppresses gassing of the lithium-ion battery, and ensures superior cycle performance and rate performance of high-capacity batteries.
• an aspect of the present application provides a positive electrode material, including a substrate.
• the substrate includes secondary particles containing primary particles.
• a molecular formula of the substrate is Li x Ni y Co z M k Me p O r A M , 0.95 ⁇ x ⁇ 1.05, 0.50 ⁇ y ⁇ 0.98, 0 ⁇ z ⁇ 0.3, 0 ⁇ k ⁇ 0.4, 0 ⁇ p ⁇ 0.0, 1 ⁇ r ⁇ 2, 0 ⁇ m ⁇ 2, m+r ⁇ 2, M is Mn and/or Al, Me is selected from one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, or Al, and A is selected from one or more of F, Cl, or Br.
• a surface of the substrate is coated with an oxide coating layer, and the oxide coating layer includes a coating element, and the coating element is selected from one or more of Al, Ba, Zn, Ti, Zr, Mg, W, Y, Si, Sn, B, Co, or P.
• a powder resistivity ⁇ of the positive electrode material under a 12 MPa pressure is 10 ⁇ *cm-5000 ⁇ *cm, more specifically 10 ⁇ *cm-2000 ⁇ *cm.
• Another aspect of the present application provides an electrochemical energy storage apparatus, including the positive electrode material.
• the present application controls a powder resistivity of the positive electrode material to be in an appropriate range, reduces a specific surface area of the positive electrode active material, decreases the amount of residual lithium on the surface, mitigates polarization of the positive electrode material, reduces a direct current impedance of a lithium-ion battery, effectively reduces side reactions between the positive electrode material and an electrolytic solution, suppresses battery gassing, increases a volumetric energy density of the battery, and improves cycle performance and rate performance.
• a first aspect of the present application provides a positive electrode material, including a substrate.
• the substrate includes secondary particles containing primary particles.
• a molecular formula of the substrate is Li x Ni y -Co z M k Me p O r A m , 0.95 ⁇ x ⁇ 1.05, 0.70 ⁇ y ⁇ 0.98, 0 ⁇ z ⁇ 0.2, 0 ⁇ k ⁇ 0.2, 0 ⁇ p ⁇ 0.05, 1 ⁇ r ⁇ 2, 0 ⁇ m ⁇ 2, m+r ⁇ 2, M is Mn and/or Al, Me is selected from one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, or Al, and A is selected from one or more of F, Cl, or Br.
• a surface of the substrate is coated with an oxide coating layer, and the oxide coating layer includes a coating element, and the coating element is selected from one or more of Al, Ba, Zn, Ti, Zr, Mg, W, Y, Si, Sn, B, Co, or P.
• a powder resistivity ⁇ of the positive electrode material under a 12 MPa pressure is 10 ⁇ *cm-5,000 ⁇ *cm.
• a layered lithium nickel cobalt manganese oxide has a relatively high theoretical specific capacity per gram due to a high content of Ni.
• a valence state of nickel is unstable, a relative content of Ni 4+ increases with the increase of Ni. Consequently, side reactions of an electrolytic solution occur on a surface of the positive electrode material.
• the substrate in the present application includes secondary particles containing primary particles. With a surface of the substrate being coated with an oxide coating layer, the surface of the high-nickel lithium transition metal oxide is effectively passivated, the electrolytic solution is isolated, residual lithium on an active substance surface is reduced, and battery gassing is suppressed.
• the oxide used is a simple oxide of a high ion conductivity and a relatively low electron conductivity, polarization of the positive electrode material will escalate, and cycle performance of the battery will deteriorate. Therefore, in the present application, the surface of the substrate is coated with an oxide for surface modification, and a specific doping element is also applied, with a dopant dosage being optimized.
• the powder resistivity of the positive electrode material is controlled to be 10 ⁇ *cm-5,000 ⁇ cm, so that an intrinsic electron conductivity of the positive electrode material is relatively high.
• the residual lithium and other impurities on the surface are reduced. This effectively reduces side reactions between the material and the electrolytic solution, and decreases an interface resistance between the electrolytic and a positive electrode active substance. In this way, polarization of the battery is mitigated significantly, and the cycle performance and the rate performance of the battery are improved.
• a range of the powder resistivity ⁇ of the positive electrode material under a 12 MPa pressure may be: 10 ⁇ *cm-5,000 ⁇ *cm, 10 ⁇ *-3,000 ⁇ *cm, 10 ⁇ *cm-2,000 ⁇ *cm, 10 ⁇ *cm-1,000 ⁇ *cm, 10 ⁇ *cm-500 ⁇ *cm, 10 ⁇ *cm-100 ⁇ *cm, 10 ⁇ *cm-50 ⁇ *cm, 10 ⁇ *cm-30 ⁇ *cm, 30 ⁇ *cm-50 ⁇ *cm, 50 ⁇ *cm-100 ⁇ *cm, 100 ⁇ *cm-200 ⁇ *cm, 200 ⁇ *cm-300 ⁇ *cm, 300 ⁇ *cm-500 ⁇ *cm, 500 ⁇ *cm-1,000 ⁇ *cm, 1,000 ⁇ *cm-2,000 ⁇ *cm, 2,000 ⁇ *cm-3,000 ⁇ *cm, or
• the powder resistivity of the positive electrode active substance under a 12 MPa pressure may be measured by using a known powder resistivity measurement method.
• the powder resistivity of the positive electrode active substance under a 12 MPa pressure is measured by using a four-probe method.
• the test method includes: adding 0.4 g of positive electrode active substance powder to a sample mold (with an inner diameter of 11.28 mm); using a mechanical press to exert a 12 MPa pressure on the powder; and reading, after the pressure is stable, the powder resistivity of the positive electrode active substance under a 12 MPa pressure by using a resistivity meter.
• a content My of the coating element per unit volume of the positive electrode material may be 400 ⁇ g/cm 3 -15,000 ⁇ g/cm 3 , 400 ⁇ g/cm 3 -12,000 ⁇ g/cm 3 , 800 ⁇ g/cm 3 -10,000 ⁇ g/cm 3 , 400 ⁇ g/cm 3 -600 ⁇ g/cm 3 , 600 ⁇ g/cm 3 -800 ⁇ g/cm 3 , 800 ⁇ g/cm 3 -1,000 ⁇ g/cm 3 , 1,000 ⁇ g/cm 3 -2,000 ⁇ g/cm 3 , 2,000 ⁇ g/cm 3 -4,000 ⁇ g/cm 3 , 4,000 ⁇ g/cm 3 -6,000 ⁇ g/cm 3 , 6,000 ⁇ g/cm 3 -8,000 ⁇ g/cm 3 , 8,000 ⁇ g/cm 3 -10,000 ⁇ g/cm 3 , 10,000
• the content My of the coating element per unit volume of the positive electrode material is 800 ⁇ g/cm 3 -10,000 ⁇ g/cm 3 .
• the present application both ensures surface modification effects of the secondary particles and suppresses polarization of the positive electrode material in a system in which particles of different sizes are distributed, effectively suppresses gassing of a high-capacity battery, and improves the cycle performance and the rate performance.
• a ratio of the powder resistivity ⁇ of the positive electrode material to the content My of the coating element per unit volume of the positive electrode material satisfies: ⁇ /Mv ⁇ 1 ( ⁇ *cm 4 / ⁇ g), ⁇ /Mv ⁇ 0.8 ( ⁇ *cm 4 / ⁇ g), ⁇ /Mv ⁇ 0.6 ( ⁇ *cm 4 / ⁇ g), or ⁇ /Mv ⁇ 0.5 ( ⁇ *cm 4 / ⁇ g).
• the unit of the powder resistivity of the positive electrode material may be ⁇ *cm
• the unit of the content of the coating element per unit volume of the positive electrode material may be ⁇ g*cm ⁇ 3 .
• the lower the ratio of ⁇ /Mv the higher the content of the coating element, the less the overall polarization of the positive electrode material, the fewer the side reactions, and the better the cycle performance.
• the coating element is selected from at least, two or more of Al, Ba, Zn, Ti, Zr, Mg, W, Y, Si, Sn, B, Co, P, or the like.
• the surface of the substrate may be coated with an oxide coating layer.
• the oxide coating layer may be located on the surface of the secondary particles.
• the coating element in the oxide coating layer may be distributed on the surface of the secondary particles.
• the coating element may exist in the form of an oxide thereof.
• the oxide coating layer may include an oxide formed by at least two coating elements described above, thereby increasing stability of adhesion of a coating layer to the surface of the substrate, achieving both ion conductivity and electron conductivity of the coating layer, and reducing the impact of the coating layer on the polarization of the positive electrode material. This effectively avoids direct contact between a high-nickel substrate and the electrolytic solution, reduces the side reactions between the substrate and the electrolytic solution, avoids a large amount of gas generated during cycles, and ensures a relatively low impedance and superior cycle performance and rate performance of the battery.
• the coating element is distributed on the surface of at least a part of the primary particles inside the secondary particles, and this part of the coating element may exist in the form of an oxide thereof.
• the coating element may also be distributed at a grain boundary between adjacent primary particles, and this part of the coating element may exist in the form of an oxide thereof.
• a secondary particle is formed by closely packing several primary particles. During a cycle, the secondary particles expand and contract in volume, thereby increasing spacing between the primary particles in the secondary particles, exposing uncoated fresh surfaces massively, and thus posing risks of side reactions with the electrolytic solution.
• the surface of the secondary particles is coated with a coating layer, and a further coating is formed on the surface of at least a part of the primary particles inside the secondary particles or at the grain boundary between adjacent primary particles, thereby enhancing an internal packing density of the secondary particles, increasing an internal acting force between the primary particles, and further suppressing battery gassing during cycles.
• the content of the coating element in the oxide coating layer may be at least 60 wt %, at least 70 wt %, at least 80 wt %, or at least 90 wt % of the total mass of the coating element in the positive electrode active material, more specifically 80 wt %-98 wt %.
• the surface of the secondary particles contacts the electrolytic solution first and has a relatively larger surface area. Therefore, when the mass of the coating element distributed on the surface of the secondary particles accounts for a specific percentage or a higher percentage in the total mass of the coating element in the positive electrode active material, the surface of the high-nickel positive electrode material is modified significantly, and the effect of suppressing battery gassing is superior.
• the positive electrode material provided in the present application is a lithium transition metal oxide.
• the lithium element In a preparation process, a specific content of elements is segregated. Therefore, in the molecular formula of the positive electrode material, the lithium element may be deficient or rich in lithium to some extent.
• a relative content of the lithium element is 0.95 ⁇ x ⁇ 1.05, little impact is exerted on the capacity of the positive electrode material.
• the relative content of the lithium element may be 0.95 ⁇ x ⁇ 1, or 1 ⁇ x ⁇ 1.05.
• the substrate is a lithium transition metal oxide with a higher nickel content.
• the substrate may be LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.5 Co 0.25 Mn 0.25 O 2 , LiNi 0.55 Co 0.15 Mn 0.3 O 2 , LiNi 0.55 Co 0.1 Mn 0.35 O 2 , LiNi 0.55 Co 0.05 Mn 0.4 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.75 Co 0.1 Mn 0.15 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.85 Co 0.05 Mn 0.1 O 2 , LiNi 0.88 Co 0.05 Mn 0.07 O 2 , LiNi 0.9 Co 0.05 Mn 0.05 O 2 , or a material obtained by partially substituting or modifying the foregoing substance with Me and/or A, where Me is selected from one or more of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, or Al, and A is
• a positive electrode active material that contains a relatively high nickel content is selected as the positive electrode active material in the present application.
• the theoretical specific capacity per gram of the material is higher, and can effectively increase the volumetric energy density of the battery.
• the present application effectively solves the gassing problem of high-capacity batteries during cycles and increases the energy density and service life of the batteries.
• the substrate of the positive electrode material in the present application is a lithium nickel cobalt manganese oxide with a Ni content of 0.80-0.98
• the residual lithium content on the surface is higher. Therefore, the content of the coating layer needs to be increased, or the coating layer needs to be a metal oxide that is more inert.
• the impact on the impedance of the positive electrode material is more significant if the content of the coating layer is increased or the coating layer is a metal oxide that is more inert.
• the Dv50 of the secondary particles may be 5 ⁇ m-18 ⁇ m, and a particle diameter range of the primary particles may be 0.1 ⁇ m-1 ⁇ m.
• the Dv50 generally means a particle diameter existent when a cumulative volume distribution percentage of a sample reaches 50%.
• the Dv50 of the secondary particles may be 5 ⁇ m-18 ⁇ m, 6 ⁇ m-15 ⁇ m, 8 ⁇ m-14 ⁇ m, 9 ⁇ m-11 ⁇ m, 10 ⁇ m-12 ⁇ m, 12 ⁇ m-14 ⁇ m, 14 ⁇ m-16 ⁇ m, or 16 ⁇ m-18 ⁇ m.
• the particle diameter range of the primary particles may be 0.1 ⁇ m-1 ⁇ m, 0.1 ⁇ m-0.9 ⁇ m, 0.2 ⁇ m-0.8 ⁇ m, or 0.2 ⁇ m-0.5 ⁇ m.
• a specific surface area of the positive electrode material is 0.1 m 2 /g-0.8 m 2 /g.
• the specific surface area of the positive electrode material may be 0.1 m 2 /g-0.8 m. 2 /g, 0.1 m 2 /g-0.2 m 2 /g, 0.2 m 2 /g,-0.3 m 2 /g, 0.3 m 2 /g-0.4 m 2 /g, 0.4 m 2 /g-0.5 m 2 /g, 0.5 m 2 /g-0.6 m 2 /g 0.6 m 2 /g-0.7 m 2 /g, or 0.7 m 2 /g-0.8 m 2 /g.
• an average particle diameter and a Brunauer-Emmett-Teller (BET) specific surface area of the positive electrode material are set within the above range to effectively reduce the contact area between the positive electrode material and the electrolytic solution. Even under the effect of a high voltage or high oxidization, few side reactions of the electrolytic solution occur on the surface of the positive electrode active substance. This effectively suppresses battery gassing, reduces heat emission, and effectively improves the safety performance and the cycle performance of the batteries. In addition, a path for intercalating and deintercalating lithium ions in the particles of the positive electrode active substance during charging and discharging is not too long, thereby further improving kinetic performance of the batteries.
• BET Brunauer-Emmett-Teller
• the content of Li 2 CO 3 in the residual lithium on the surface of the positive electrode material is less than 3,000 ppm.
• the content of Li 2 CO 3 in the residual lithium is less than 2,000 ppm.
• the content of LiOH in the residual lithium on the surface of the positive electrode material is less than 5,000 ppm.
• the content of LiOH in the residual lithium is less than 4,000 ppm.
• the substrate of the positive electrode material in the present application is a lithium nickel cobalt manganese oxide that contains a high nickel content, and generally a relatively high residual lithium content exists on the surface of the substrate.
• the coating layer disposed on the surface of the substrate effectively reduces the residual lithium content on the surface, but leads to much polarization of the positive electrode material.
• the positive electrode material with a residual surface lithium content falling within the above range effectively mitigates gassing and polarization, and achieves a high-capacity battery with insignificant gassing and superior cycle performance and rate performance.
• the content of Li 2 CO 3 in the residual lithium on the surface of the positive electrode material is less than the content of LiOH.
• the residual surface lithium LiOH, Li 2 O
• the higher the Li 2 CO 3 content the more violent the reaction, and the severer the gassing problem of the manufactured battery.
• a second aspect of the present application provides a method for preparing the positive electrode material according to the first aspect of the present application.
• the method includes:
• the method for preparing the positive electrode material according to the present application may include: providing a substrate.
• the method for providing the substrate is known to those skilled in the art.
• the method for providing the substrate may include: mixing and sintering ingredients of the substrate to generate the substrate.
• the ingredients of the substrate may include a ternary material precursor of nickel, cobalt, manganese and/or aluminum, a lithium source, an M source, an Me source, an A source.
• the ratio between the ingredients is generally determined with reference to the ratio between the elements in the substrate.
• the ternary material precursor may be, but without limitation, Ni 0.5 Co 0.2 Mn 0.3 (OH) 2 , Ni 0.5 Co 0.25 Mn 0.25 (OH) 2 , Ni 0.55 Co 0.15 Mn 0.3 (OH) 2 , Ni 0.55 Co 0.1 Mn 0.35 (OH) 2 , Ni 0.55 Co 0.05 Mn 0.4 (OH) 2 , Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 , Ni 0.75 Co 0.1 Mn 0.15 (OH) 2 , Ni 0.8 (Co 0.1 Mn 0.1 (OH) 2 , Ni 0.88 Co 0.05 Mn 0.07 (OH) 2 , 0.9Ni 0.8 Co 0.2 (OH) 2 .0.1Al 2 (OH) 3 , or 0.9Ni 0.9 Co 0.5 Mn 0.05 (OH) 2 .0.1Al 2 (OH) 3 .
• the lithium source may be a lithium-containing compound.
• the lithium-containing compound may be, but without limitation, one or more of LiOH ⁇ H 2 O, LiOH, Li 2 CO 3 , Li 2 O.
• the Me source may be a compound containing an Me element.
• the compound containing an Me element may be one or more of an oxide, a nitrate, or a carbonate, each containing at least one of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, or Al.
• the A source may be a compound containing the A element.
• the compound containing the A element may be, but without limitation, one or more of LiF, NaCl, or NaBr.
• conditions of the sintering may be 800° C. and an oxygen concentration greater than or equal to 20%.
• the method for preparing the positive electrode material according to the present application may further include: forming a coating layer on the surface of the substrate.
• the method for forming a coating layer on the surface of the substrate is known to those skilled in the art.
• the method for forming a coating layer on the surface of the substrate may include: sintering the substrate under a condition that a compound containing a coating element exists, so that a coating layer is formed on the surface of the substrate.
• Those skilled in the art may, according to the composition of the coating layer and parameters such as the powder resistivity of the substrate, select appropriate types, mixing ratios, sintering conditions, and the like of the compound containing the coating element.
• the compound containing the coating element may be, but without limitation, one or more of Al 2 O 3 , ZnO, ZrO 2 , TiO 2 , MgO, WO 3 , Y 2 O 3 , Co 2 O 3 , Ba(NO 3 ) 2 , Co 2 O 3 , P 2 O 5 , or H 3 BO 3 .
• the dosage of the coating element may be 0.01 wt %-0.5 wt % of the mass of the substrate.
• the sintering condition may be high-temperature sintering under 200° C.-700° C.
• a third aspect of the present application provides an electrochemical energy storage apparatus, including the positive electrode positive material according to the first aspect of the present application.
• the electrochemical energy storage apparatus may be a super capacitor, a lithium-ion battery, a lithium metal battery, a sodium-ion battery, or the like, in the embodiments of the present application, only an embodiment in which the electrochemical energy storage apparatus is a lithium-ion battery is described, but the present application is not limited thereto.
• the lithium-ion battery may include a positive electrode plate, a negative electrode plate, a separator located between the positive electrode plate and the negative electrode plate, and an electrolytic solution.
• the positive electrode plate includes the positive electrode active material according to the first aspect of the present application.
• the method for preparing the lithium-ion battery is known to a person skilled in the art.
• the positive electrode plate, the separator, and the negative electrode plate may each be a laminate, so as to be suitable for being stacked sequentially after being cut to a target size.
• the laminate may be wound to a target size to form a battery cell, and may be further combined with the electrolytic solution to form a lithium-ion battery.
• the positive electrode plate generally includes a positive electrode current collector and a positive electrode material layer located on the positive electrode current collector.
• the positive electrode material layer may include a positive electrode active material according to the first aspect of the present application, a binder, and a conductive agent.
• a person skilled in the art may choose an appropriate method to prepare the positive electrode plate.
• the method may include the following steps: mixing the positive electrode active material, the binder, the conductive agent to form a slurry, and coating the positive electrode current collector with the slurry.
• the binder generally includes a fluorine-containing polyolefin-based binder. Compared with the fluorine-containing polyolefin-based binder, water is generally a good solvent.
• the fluorine-containing polyolefin-based binder is generally highly soluble in water.
• the fluorine containing polyolefin-based binder may be, but without limitation, polyvinylidene fluoride (PVDF), a vinylidene fluoride copolymer, or a modified derivative thereof (for example, modified carboxylic acid, acrylic acid, or acrylonitrile).
• PVDF polyvinylidene fluoride
• a vinylidene fluoride copolymer or a modified derivative thereof (for example, modified carboxylic acid, acrylic acid, or acrylonitrile).
• a mass percent content of the binder may be a specific value. Due to a low conductivity of the binder itself, the dose of the binder needs to be not too high.
• the mass percent content of the binder in the positive electrode active substance layer is less than or equal to 2 wt %, so as to achieve a relatively low electrode plate impedance.
• the conductive agent of the positive electrode plate may be any of various conductive agents applicable to a lithium-ion (secondary) battery in this field.
• the conductive agent may be, but without limitation, one or more of acetylene black, conductive carbon black, vapor grown carbon fiber (VGCF), or Ketjen black.
• the weight of the conductive agent may be 1 wt %-10 wt % of the total mass of a positive electrode material layer. Desirably, a weight ratio of the conductive agent to the positive electrode active substance in the positive electrode plate is greater than or equal to 1.5:95.5.
• the positive electrode current collector of the positive electrode plate generally may be a laminate.
• the positive electrode current collector is generally a structure or part that can collect current.
• the positive electrode current collector may be any of various materials suitable for use as a positive electrode current collector of a lithium-ion battery in this field.
• the positive electrode current collector may be, but without limitation, a metal foil. More specifically, the positive electrode current collector may be, but without limitation, a copper foil or an aluminum foil.
• the negative electrode plate generally includes a negative electrode current collector and a negative electrode active substance layer located on a surface of the negative electrode current collector.
• the negative electrode active substance layer generally includes a negative electrode active substance.
• the negative electrode active substance may be any of various materials suitable for serving as a negative electrode active substance of a lithium-ion battery in this field, for example, may be but without limitation one or more of graphite, soft carbon, hard carbon, vapor grown carbon fiber, mesocarbon microbead, silicon-based material, tin-based material, lithium titanate oxide, or other metals that can combine with lithium into an alloy.
• the graphite may be selected from one or more of artificial graphite, natural graphite, or modified graphite.
• the silicon-based material may be selected from one or more of elemental silicon, a silicon-oxygen compound, a silicon-carbon composite, or a silicon alloy.
• the tin-based material may be selected from one or more of elemental tin, a tin-oxide compound, or a tin alloy.
• the negative electrode current collector is generally a structure or part that collects current.
• the negative electrode current collector may be any of various materials suitable for use as a negative electrode current collector of a lithium-ion battery in this field.
• the negative electrode current collector may be, but without limitation, a metal foil. More specifically, the negative electrode current collector may be, but without limitation, a copper foil.
• the separator may be any of various materials suitable for use as a separator of a lithium-ion battery in this field.
• the separator may be, but without limitation, one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid fiber, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, or natural fiber.
• the electrolytic solution may be any of various electrolytic solutions applicable to the lithium-ion battery in this field.
• the electrolytic solution generally includes an electrolyte and a solvent.
• the electrolyte may generally include a lithium salt and the like.
• the lithium salt may be an inorganic lithium salt and/or an organic lithium salt or the like.
• the lithium salt may be, but without limitation, one or more of LiPF 6 , LiBF 4 , LiN(SO 2 F) 2 (LiFSI for short), LiN(CT 3 SO 2 ) 2 (LiTFSI for short), LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (LiBOB for short), or LiBF 2 C 2 O 4 (LiDFOB for short).
• a concentration of the electrolyte may be 0.8 mol/L-1.5 mol/L.
• the solvent may be any of various solvents applicable to the electrolytic solution of the lithium-ion battery in this field.
• the solvent of the electrolytic solution is generally a nonaqueous solvent, exemplarily an organic solvent.
• the solvent may be, but without limitation, one or more of ethylene carbonate, propylene carbonate, butyllene carbonate, pentene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, or a halogenated derivative thereof.
• a combination of one or more method steps mentioned in the present application shall not preclude other method steps existent before or after the combination of steps, or preclude other method steps from being inserted between the explicitly mentioned steps.
• a combination or connection relationship between one or more devices/apparatuses mentioned herein shall not preclude other devices/apparatuses existent before or after the combined devices/apparatuses, or preclude other devices/apparatuses from being inserted between two devices/apparatuses explicitly mentioned herein.
• reference numerals of the method steps are intended only for ease of identification rather than for limiting the arrangement order of the method steps or for limiting the scope of applicability of the present application. Any change or adjustment to the relative relationship between the reference numerals shall fall within the scope of applicability of the present application to the extent that no substantive change is made to the technical content hereof.
• Step 1 Preparing a Substrate Precursor.
• Step 2 Placing the substrate precursor prepared in step 1, an Li-containing compound, an Me-containing compound, and a Y-containing compound in a mixing device for mixing, and then placing the mixture in a controlled atmosphere furnace for sintering to obtain a substrate of a positive electrode material.
• Step 3 Placing the substrate of the positive electrode active material and a specific content of a compound that contains a coating element into a mixing device for mixing, and then placing the mixture in a controlled atmosphere furnace for sintering to form a coating layer of the positive electrode active material, thereby obtaining a finished positive electrode material.
• Step 1 Mixing the positive electrode material, polyvinylidene fluoride as a binder, and acetylene black as a conductive agent at a mass ratio of 98:1:1, adding the mixture into an N-methylpyrrolidone (NMP) solvent, and homogeneously stirring the mixture with a vacuum mixer to obtain a positive electrode slurry; and coat an electrode plate with the positive electrode slurry homogeneously until an areal density reaches 0.1 mg/mm 2 -0.3 mg/mm 2 .
• NMP N-methylpyrrolidone
• Step 2 Drying the coated electrode plate in a 100° C.-130° C. oven, and performing cold calendering and slitting to obtain a positive electrode plate.
• an organic solvent that is a mixed solution containing vinylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), where a volume ratio between the EC, the EMC and the DEC is 20:20:60.
• EC vinylene carbonate
• EMC ethyl methyl carbonate
• DEC diethyl carbonate
• step (1) above in which the positive electrode material is prepared specific steps are as follows:
• the particle diameter of particles is controlled by controlling a reaction time, a pH value during co-precipitation, and an ammonia concentration.
• Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 and a lithium-containing compound LiOH ⁇ H 2 O into a mixing device for mixing, and then leaving the mixture in a controlled atmosphere furnace for sintering under 800° C.; cooling the mixture, and grinding the mixture mechanically to obtain a substrate of the ternary material; placing the substrate of the positive electrode active material and a 0.3 wt % Al 2 O 3 additive in the mixing device for mixing, and then leaving the mixture in the controlled atmosphere furnace for sintering under 450° C. to form a coating layer of the positive electrode active material, so that a finished material is obtained.
• the preparation method of the positive electrode material in Embodiments 2-14 is basically the same as that in Embodiment 1 except the following: using a different relative content of Ni, Co, Mn, and Al elements in the precursor to prepare a substrate of different components; adjusting the reaction time, the pH value during co-precipitation, and the ammonia concentration, and changing the size of the primary particles and the secondary particles; and changing the types of substances in the coating layer, the content of the coating layer, and a heat treatment temperature.
• the specific characteristics of the positive electrode material in the foregoing embodiments are shown in Table 1. Finally, the positive electrode material in Embodiments 2-14 is obtained.
• Comparative Embodiment 1 The preparation method in Comparative Embodiment 1 is similar to that in Embodiment 1 described above, except that the surface of a sample in the comparative embodiment is coated with V 2 O 5 .
• Comparative Embodiment 2 The preparation method in Comparative Embodiment 2 is similar to that in Embodiment 17 described above, except that the surface of a sample in the comparative embodiment is coated with Fe 2 O 3 .
• Comparative Embodiment 3 The preparation method in Comparative Embodiment 3 is similar to that in Embodiment 17 described above, except that in the sample coating process in the comparative embodiment, the sintering temperature of the added Al 2 O 3 additive is 600° C.
• the test method includes: adding 0.4 g of positive electrode active substance powder to a sample mold (with an inner diameter of 11.28 mm); using a mechanical press to exert a 12 MPa, pressure on the powder; and reading, after the pressure is stable, the powder resistivity of the positive electrode active substance under a 12 MPa pressure by using a resistivity meter.
• Table 1 shows test results in Embodiments 1-14 and Comparative Embodiments 1-3.
• the discharge capacity of the lithium-ion battery with the positive electrode material in Embodiments 1-14 is basically the same as that in Comparative Embodiments 1-3
• the powder resistivity of the positive electrode material in Embodiments 1-14 is significantly lower than that in Comparative Embodiments 1-3. Therefore, the cycle performance of the corresponding lithium-ion battery is significantly higher than that in Comparative Embodiments 1-3.
• the type of the coating material, the content of the coating element per unit volume, and the preparation process of the coating layer exert an impact on an ion conductivity and an electron conductivity of the coating layer, and on a surface status of the positive electrode material, and exert a great impact on the powder resistivity of the positive electrode material.
• the powder resistivity of the positive electrode material is further improved, and the cycle performance of the lithium-ion battery is further enhanced.
• the two coatings are homogeneously distributed on the surface of the positive electrode material to preclude side reactions between the positive electrode material and the electrolytic solution. This also ensures a low powder resistivity of the positive electrode material, enhances surface stability, causes the surface of the positive electrode material to be both highly ion-conductive and highly electron-conductive, and achieves better cycle performance.

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